Experts used to believe that mental decline was something exclusive to the elderly and aging. New research now shows certain brain function begins to deteriorate much sooner - in the late 20s and 30s. Those brain functions susceptible to early deterioration included mental speed, problem solving and abstract reasoning. However, things such as vocabulary and general knowledge improved with age due to the accumulation of knowledge that occurs over the years. The new findings allow researchers to better study cognitive changes as we age and help to potentially discover ways to slow the deterioration as well as better predict the onset of dementias including Alzheimer's Disease.